Estimating coolant conductivity in a multi-voltage fuel cell system

摘要

A coolant conductivity method and apparatus used to determine when a coolant, circulating through a vehicle's coolant system, starts to conduct electrical current and loses its electrical isolation properties. The system includes a battery monitor controller senses one or more isolation resistances placed throughout a fuel cell system and is programmed to run an isolation algorithm. The isolation algorithm opens and closes contactors in a specific order, measures the resistance of the one or more isolation resistances and calculates a coolant conductivity value. The system will indicate when the coolant needs to be replaced.

主权项

1. A method for monitoring coolant conductivity in a coolant system that is used to provide thermal management of a fuel cell stack, comprising:
closing at least one contactor in an electrical system comprising a stack voltage and a battery voltage; measuring a first isolation value, a second isolation value, the stack voltage, and the battery voltage; opening the at least one contactor in the electrical system; measuring a first negative isolation value; calculating a stack isolation resistance using the first isolation value, the second isolation value, the first negative isolation value, the stack voltage, and the battery voltage; calculating a coolant conductivity value; and providing indicia that a coolant needs to be replaced when the coolant conductivity value crosses a threshold value.